A bis(silatranylalkyl) polysulfide and a method for manufacturing thereof are known from the published literature (see Patent Literature 1 (Japanese Unexamined Patent Application Publication {hereinafter referred to as “Kokai”} S50-108225, i.e., JP50-108225A), Patent Reference 2 (Kokai S60-33838, i.e., JP60-33838A), and Patent Reference 3 (Kokai 2001-31798, i.e., JP 2001-31798A)).
Example 13 added to the specification of Patent Reference 2 after the publication of the application describes synthesis of a bis(silatranylpropyl) tetrasulfide by mixing 2 moles of a silatranylpropylmercaptane with 3 moles of a sulfur powder under heating conditions.
This synthesis develops hydrogen sulfide, which normally is in a gaseous state and is characterized by very high toxicity. Therefore, the aforementioned method is associated with such problems as the use of synthesis equipment that prevents leakage of the generated hydrogen sulfide into the environment and the necessity of constantly wearing an antitoxic mask.
Example 13 of Patent Reference 2 describes a synthesized bis(silatranylpropyl) tetrasulfide, which is a white crystalline substance having no melting point. SILATRAN (OS34=Si79), which is the same as the aforementioned bis(silatranylpropyl) tetrasulfide, were mixed with a natural rubber, active silicic acid, or the like, the mixture was vulcanized, and physical properties of the product were measured. However, since the bis(silatranylpropyl) tetrasulfide is a crystalline substance having no melting point, dispersion thereof in such substances as a natural rubber or synthetic rubber and a silica filler presents a problem, even when the mixture is kneaded with application of a shear force, e.g., in a two-roll mill.